Liquid water diffusivity of wood from the capillary pressure-moisture relation |
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Authors: | Wook Kang Woo Yang Chung |
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Institution: | (1) Department of Wood Science and Engineering, Division of Forest Resources and Landscape Architecture, Chonnam National University, Gwangju, 500-757, Republic of Korea |
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Abstract: | This study focuses on liquid water transport in wood above the fiber saturation point in the nonhygroscopic region. The liquid
water transport of hygroscopic porous materials including wood is usually described by Darcy’s law. It requires knowledge
of capillarity and intrinsic and relative permeabilities. In this study, the capillary pressure-water relation and relative
permeability were investigated using experimental data for wood available in the literature. The performance of three models
(Brooks-Corey model, van Genuchten model, and Durner’s bimodal pore-size distribution model) was investigated for the capillary
pressure-water relation. These models have advantages in that each shape parameter has qualitative physical meaning for the
pore-size distribution. Most species had unimodal pore distributions except for aspen, which had a bimodal pore distribution.
The van Genuchten model represented the capillary pressure-water relation better than the Brooks-Corey model. Durner’s bimodal
model was found to be the most appropriate for the capillary pressure-moisture relation of aspen. The relative permeability
was calculated by using Mualem’s model, which was compared with the value from the Couture model. From the results, the liquid
water diffusivity divided by intrinsic permeability of wood was estimated. This approach may be promising for adopting the
liquid water diffusivity for the numerical simulation of drying and sorption, although there might be considerable variation
within and between trees. |
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Keywords: | Liquid water transport Capillary pressure Permeability Wood Nonlinear fitting |
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